Looking at his debut season's record is a little disingenuous. He had the 5th most inexperienced team in the nation and was picked to finish last in the CUSA. They finished 6th (8-8). That's a pretty significant overachievement. I get that the loss to Oral Roberts (and the subsequent loss at Missouri State) looks bad. It is bad. The team was a mess at the start of the season, for whatever reason, but they really did turn it around.
In terms of raw results, I'm not discouraged by anything Manning accomplished at Tulsa. Granted, I'm not really encouraged either (the resume is still very thin, regardless of what's on it), but I don't see many reasons to project outright failure from his time over there.